Table 1.
Known characterized N-oxidases and their homology to HpxL, which is encoded by the hydroxyphosphonocystoximic gene cluster
PcxL is found in the homologous phosphonocystoximic biosynthetic gene cluster. FzmM and CreE catalyze the N-oxidation of aspartic acid to nitrosuccinic acid during fosfazinomycin and cremeomycin biosynthesis, respectively (22, 23). AzmF and CrmH are characterized as flavin-dependent N-oxidases that catalyze oxime formation in azolemycin and caerulomycin biosynthesis (17, 18). ClmM is the predicted FAD- and NAD(P)H-dependent N-oxidase of collismycin biosynthesis (40), and AlmD is the metal-dependent N-oxidase involved in oxime formation of alithomycin biosynthesis (16). Note that only FzmM and CreE can be considered bona fide homologs of PcxL and HpxL.
| Enzyme | NCBI accession no. | Organism | Natural product | % Identity to HpxL | E-Value | Lengtha |
|---|---|---|---|---|---|---|
| HpxL | WP_030990682.1 | S. regensis WC-3744 | Hydroxyphosphonocystoximate | 100 | 0 | 750 |
| PcxL | WP_051704824.1 | Streptomyces sp. S-481 | Phosphonocystoximate | 61 | 0 | 742 |
| AzmF | AMQ23503.1 | Streptomyces sp. FXJ1.264 | Azolemycin | 10 | 2.9 | 389 |
| ClmM | CCC55915.1 | Streptomyces sp. CS40 | Collismycin A | 9 | 1.4 | 402 |
| CrmH | AFD30961.1 | Actinoalloteichus sp. WH1-2216-6 | Caerulomycin A | 8 | 1.1 | 407 |
| AlmD | CCA29200.1 | Myxococcus xanthus DK897 | Althiomycin | 8 | 3.4 | 331 |
| FzmM | WP_053787792.1 | Streptomyces sp. XY332 | Fosfazinomycin | 30 | 6E-14 | 644 |
| CreE | ALA99202.1 | Streptomyces cremeus | Cremeomycin | 35 | 3E-29 | 666 |
a Number of amino acids.